Fix "armv8-a" architecture to support GCC 13.3rel1

SCP-firmware's "armv8-a" architecture does not currently support Arm GCC 13 as the bundled version of Newlib now requires a device-specific implementation of standard libc functions. However, the cortex-r82 CPU tune is only available in newer toolchain versions, so a toolchain upgrade is required to use a more appropriate tune for the fvp-baser-aemv8r product.

Provide the missing stubs for "armv8-a" using the same file as provided by the new AArch64 architecture and upgrade the toolchain in the development Docker container.